Valve question

I have a seven zone system, 3 of the 7 zones are functioning and the other 4 are just trickling as to where the heads won't rise. Is it possible that my diaphragm's are bad? They are Hunter PGV valves, I did not run the system very often last year.

Seems odd to have 4 failing PGV valves at the same time. Are you able to locate where all the valves are? I'm wondering if you have 3 working valves in one valve box and 4 non-working valves in another.

You can try manually turning on one of the troubled valves, see if that gets it to come on. Loosening the bleed screw should get it to pop open.